Vinylidene terminated polyolefins, such as polyisobutylene (PIB), are useful precursors for the preparation of polymers containing functional end groups. Vinylidene end groups may be transformed into other specific functional end groups. Polymers containing specific end groups have several useful purposes. For example, PIB-based succinimide dispersants are useful additives for engine lubricants, and polyisobutylene amines are useful as fuel additives. The vinylindene isomer is the most reactive isomer towards many reactions selected to transform the polyolefin chain end. Thus, there is a need for methods of selectively or exclusively producing vinylidene terminated polyolefins.
In recent years, considerable research has been conducted in the field of quasiliving cationic polymerization (QLCP) of olefins. Quasiliving polymerizations proceed with minimal chain transfer while irreversible termination is practically absent. Therefore, QLCP yields polymers with well defined architectures and narrow molecular weight distributions. Another advantage of QLCP is that it offers the potential for in situ functionalization of the polymer chain ends and block copolymer synthesis. In situ functionalization provides materials which are amenable towards further post-polymerization reactions.
Research involving in situ functionalization of QLCP has yielded a variety of end groups. However, successful production of the vinylidene terminus has been achieved in a limited number of cases. Kennedy et al. disclosed the use of allyltrimethylsilane as a quenching agent to cap PIB with an allyl group (J. Poly. Sci. A: Poly. Chem., 25, 3255, 1987). Mayer et al. illustrated a similar reaction through the use of 2-methallyltrimethylsilane to yield the exo olefin product (Macromolecules, 29, 6104, 1996). However, both of these synthetic routes utilize rather expensive reagents which are consumed in the reaction with PIB during the quenching step.
Recent work by Stokes et al., in US Patent Publication Nos. 2006/0041083 and 2006/0041084, describes the in situ conversion of quasiliving, tertiary chloride PIB chain ends to vinylidene via the use of certain nitrogen-containing quenching agents.
A need exists in the art to develop new in situ processes for producing vinylidene terminated polyolefins which offer the potential recovery of key reagents in the quenching process. Recycling of quenching agents could lead to reduced cost.